code: def start_tunnel(self) -> str:
      self.download_binary()
      self.url = self._start_tunnel(BINARY_PATH)
      return self.url
  
file_path: gradio/gradio/tunneling.py
imports: import atexit
  import os
  import platform
  import re
  import stat
  import subprocess
  import sys
  import time
  from pathlib import Path
  from typing import List
  import httpx
label_desc: Use image node_id 3 for calling the Tunnel obj's underlying member method code with example usage: obj.start_tunnel() and returns: self